1. Field of the Invention
The present invention relates to a technique of re-utilizing waste synthetic fiber and particularly to a composite material composition obtained by first crushing waste synthetic fiber without any pretreatment, subsequently opening said waste synthetic fiber into filaments, and then impregnating the filaments with a thermoplastic synthetic resin followed by kneading.
2. Description of Prior Art
Heretofore, great efforts have been made, for example, in the manufacture of interior parts of automobiles, to utilize the supply of inexpensive products so long as they do not affect mechanical properties, not to mention the effort to satisfy the required mechanical properties for them. It is for this purpose that not an expensive synthetic resin alone but a mixture of said synthetic resin with a variety of other materials is used for the reduction of material cost. In that case, it is preferred to utilize wastes to which little importance has usually been attached as mixing material, from the viewpoint not only of the cost reduction but also of the re-utilization of natural resources.
More particularly, thermoplastic synthetic resins are disadvantageous as compared with metals in their stiffness, heat resistance, dimensional stability, and flame retardancy, so that inorganic fillers have been incorporated with said resins to overcome these defects, and fibrous fillers to improve mechanical properties. Glass fiber, wood flour, and wastepaper have been principally used as said fibrous fillers.
Among these conventional fibrous fillers, the unit price per volume of glass fiber is not so inexpensive because of its high specific gravity, which results in high specific gravity of the obtained composite material in which glass fiber has been incorporated. Although composite materials obtained by the incorporation of wood flour or wastepaper in thermoplastic synthetic resins are excellent in physical properties because of its fiber-reinforcement effect, the incorporation does not result in sufficient reinforcement because the strength of the filament is only slightly higher than that of the resin and the fibers are likely to be cut in the step of kneading or processing during the manufacture.
In the conventional technique of reinforcement with fillers, synthetic fibers such as unused polyester or polyamide have been little thought of as reinforcing agent. Moreover, synthetic fiber generated as used waste fiber has been burnt as valueless waste, or reused as felt material, at the best, after being opened together with other vegetable fibers.